Colorless p{11 o{11 {11 glass with anomalous dispersion in short wavelength region

ABSTRACT

A glass having an anomalous dispersion consisting of, by weight, calculated as the component oxides of said glass, from 38 to 70% P2O5, from 1.0 to 5.0% B2O3 and from 1 to 10% Al2O3as glassforming materials, wherein the sum of the amount of said B2O3and Al2O3 is from 2 to 15%; from 4 to 38% BeO, from 2 to 17% MgO, from 0 to 10% ZnO, from 1 to 8% CaO, from 0 to 10% SrC and from 0 to 3% As2O3 as glass modifiers, wherein the sum of the amount of said BaO, MgO, ZnO, CaO, SrO and As2O3 is 51 to 60%; and from 0.05 to 4.0%, based on the total weight of said glass-forming materials and said glass modifiers, of TiO2.

United States Pate t [1 1 Izumitani et al.

[451 Aug. 7, 1973 .1 .EQL ALEQ QBLQJQLASSWIIB.

ANOMALOUS DISPERSION IN SHORT WAVELEN@LREGIOB [75] Inventors: Tetsuro Izumitani; Isao Masuda,

both of Tokyo, Japan 1,089,935 9/1960 Germany 106/47 Q OTHER PUBLICATIONS Beals, M. D.; Effects of Titanium Dioxide in Glass; in Glass Industry, Oct. 1963 pp. 569-573 Primary ExaminerHe1en M. McCarthy Attorney-Sughrue, Rothwell, Mion, Zinn & MacPeak [30] Foreign Application Priority Data [57] ABSTRACT Mar. 2, 1970 Japan 45/17757 A glass having an anomalous dispersion consisting of, [52] Cl n 106/47 Q 65/134 106/47 R by weight, calculated as the component oxides of said [51] Im. Cl. coic 3/02 c03 3/16 38 70% P2051001 50% Bzoaand [58] Field of Search 106/47 o 47 R 50 {mm 1 glass-10mins materials wherein the sum of the amount of said B O and A1 0 [56] References Cited is from 2 to from 4 to 38% BeO, from 2 to 17% MgO, from 0 to 10% ZnO, from 1 to 8% CaO, from 0 UNITED STATES PATENTS to 10% SrC and from 0 to 3% AS 0 as glass modifiers, vwvelssenlgerg 106/47 Q wherein the sum of the amount of said BaO, MgO, 7777774 1 zzzzzg g z: 2 106/47 Q ZnO, CaO, SrO and As O is 51 to 60%; and from 0.05 7/1954 weissenberg 106/47 0 to 4.0%, based on the total weight of said glass-forming OREI AT TS S materials and said glass modifiers, of TiO,.

F GN P EN OR A L1 1 N 388,459 8/1963 Japan 106/47 Q 7 Claims, 2 Drawing Figures I cr z 2 0.500 m c: m 25 5 0.480

1 S g; 0.460 a.

1 i I I i l i i i 1 B i 60 6O l ABBE s NUMBER (1 d 1 PARTIAL DISPERSION RATIO (hg) AT g-h LINE PATENTEU I 3.751.272

FIGI

T 1 T I 2s so 00 05 v0 ABBE'S NUMBER (MI INVENTORS TETSURO IZUMITANI ISAO MASUDA su km w m Y ZLIAIA W ATTORNEYS 1 COLORLESS P,O GLASS WITH ANOMALOUS DISPERSION IN SHORT WAVELENGTH BACKGROUND OF THE INVENTION 1. Field of the Invention:

This invention relates to an optical glass having an anomalous dispersion in a short wavelength region which has a large Abbes number and a large partial dispersion ratio in the short wavelength region (generally about 250 to 500 mp.) as compared with normal dispersion glass having a linear relationship between its Abbe's number and partial dispersion ratio; and to a process for the production of such optical glass.

2. Description of the Prior Art:

The need for superachromatic lenses has increased with advances in color photographic techniques. The principle used in designing such lenses consists of removing chromatic aberration at the C- and F-lines, and causing the remaining chromatic aberration, i.e., secondary spectrum, to approach zero in the widest possible range of wavelengths. In normal dispersion glass in which, as shown in the attached FIG. 1, the relationship between Abbes number v,, and the partial dispersion ratio 0, (at the g-h line), for example, exists substantially on the straight line AB, the secondary spectrum cannot be reduced over a wide range of wavelengths as is seen from the results obtained by determination using Kfinig's of I-Iardings method.

Accordingly, this has led to the demand for anomalous dispersion glass having a different partial dispersion ratio versus Abbe's number from normal dispersion glass in the production of superachromatic lenses. Since particular emphasis is put on achromatization in a short wavelength region in view of the photosensitive wavelength region of a photosensitive material or the degree of dispersion of its refractive index, optical glass having an anomalous dispersion in a region near ultraviolet has been desired.

The partial dispersion ratio may be expressed as follows:

("q "r/"P "c) ("It "n "F "CL ("1 fl l" "c),

or the like. Since any of these expressions shows a substantially equal tendency, the anomalous dispersion in the present invention will be shown in terms of the partial dispersion ration at the g-h line [6,,,=(n,, u,,)/(n "c) l Various experiments were performed with a view to obtaining the aforementioned anomalous dispersion glass, and led to the discovery that such glass can be produced by using P,O, as a basic glass-forming material and TiO, as an additive. The presence of Ti ions, however, causes some difficulties such as blue violet coloration of the glass or poor meltability. Although such difficulties are known to be'overcome to some extent by adding large quantities of alkali oxides thereto, the use of these compounds renderes the stability of the glass extremely poor and remarkably reduces the viscosity of the glass at the time of melting which in turn leads to susceptibility to devitrification and difficulty of forming or fabrication. The chemical durability of the glass is also worsened.

It is therefore an object of the present invention to provide a colorless optical glass free of alkali ingredients, which has the desired anomalous dispersion and superior stability, meltability and chemical durability.

SUMMARY or THE INVENTION The optical glass of the present invention is produced from a glass batch consisting of, by weight, calculated as component oxides of glass, 38-70% P 0 1.0 5.0% 8,0; and l 10% M 0 as glass-forming materials, the sum of the B 0 and M 0; content being 2 15%; 4 38% BaO, 2 l7% MgO, 0 l0% ZnO, O 8% CaO, 0 10% S10, and 0 3% As,0;as glass modifiers, the sum of the BaO, MgO, ZnO, CaO, SrO, and As O content being 15 60%; and 0.05 4.0%, based on the total weight of said glass-forming materials and glass modifiers, of TiO,. The optical glass of the invention has a v, of about 45 to and a 0, of about 0.430 to 0.505.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graphic representation showing the relationship between Abbes number v and the partial dispersion ratio 0 at the line both in conventional normal dispersion glass and the anomalous dispersion glass of the present invention. The relationship shown in the former is plotted as the solid circles, while that in the latter as hollow circles.

FIG. 2 shows anexample of an anomalous dispersionof conventional anomalous dispersion glass at area X, and that of the glass of the present invention at area Y. Glass having an anomalous dispersion shown by Y has been desired in the past.

DESCRIPTION OF THE PREFERRED EMBODIMENTS P 0 has a basic absorption ina short wavelength region apart from the visible region, and therefore has a gentle curve showing the dispersion of refractive indit ces versus wavelengths in the visible region and also a large Abbes number. This makes it possible to add P,O, in somewhat greater quantities, but a suitable amount is from 38 to 70% by weight. If the amount is smaller than this range, the Abbe's number of the resulting glass becomes too small, and amounts in excess of this range result in the narrowing of the vitrification range and poor stability of the glass.

TiO,, on the other hand, has its basic absorption in an ultraviolet region near the visible region, and its addition affects the dispersion curve. But if it is added in an amount of 0.05 to 4.0% by weight based on the total amount of the other glass ingredients, its influence appears only in a region of relatively short wavelengths (about 250 to 500 mp), and not so much in a visible region around the C- and F-lines. Hence, the addition of TiO, serves to impart anomalous dispersion by rendering the dispersion ratio in an ultraviolet region relatively large without decreasing the Abbe's number.

When TiO, is added to ho -rich glass as described above, a slight absorption over a wide range in the vicinity of a wavelength of 580 my. occurs, and the glass is colored blue violet. This coloration is due to the absorption inherent to Ti ions converted from Ti ions. Alkali oxides have been found inadequate to prevent such coloration. In the present invention, the coloration is prevented by adding 1.0 5.0% by weight of 8,0,, and l l0% by weight of Al,0 (the sum of 8,0 and Al O being 2 15% by weight) to the glass batch so that the total amount of the glass-forming materials will be 40 by weight. This also improves the stability or chemical durability of glass. These properties CaO AS203 ZnO BaO SrO Tioz riae and Clmin tortionof the glass,

can be procing optical phosphate glass. For example, the following materials may be used as sources for the respective ingredients ,330" C for about 30 A520: (Pa)z ,280 to l stirred and refined to render the quality of glass uniform with the removal of st ZnO ?:(1001, SI'(PO:)2.-

C/hr. For removing the d annealing rates are preferred, and therefore,

based on the total amount of other materials.

Ca;(PO4)2 BatPOz):

The optical glass of the present invention duced by any well-known method of produ These materials in the amounts specified above in terms of the amounts of the respective oxide ingredi- Specific examples of the composition of'a glass batch according to the present invention are given in Table Table 2 shows the amounts of the raw materials given in Table I calculated as the component oxides of the glass. I I

1. In the table, the amount of TiO, is expressed in perbelng centages 3 8%, and 0.5 2.5% TiO, has especially superior sta Source Materials 7 XI3POJ and phosphates below.. aB a,

MKCOQ, MgO CaCO Ca(Ol[)1, 0:10,

and B 00 B P0 B (PO n g at, s( 01, B a)1 MgO needs to be used in a large amount. in conjunction with other divalent ingredients, MgO increases the stability of the cuts were melted at l minutes to 2 hours in a platinum crucible, ceramic crucible or clay crucible bubbles. The glass is then annealed at a rate of 2 to 10 0 lower clfied rates outside the aforesaid range can be used.

' TABLE 1 Raw materials (percent by weight) 11,90. BIO; AlPOi Mg(PO;)1

and amounts outside the s ranges do not give sufficient results in improving the various properties mentioned above. ight, P,O,, l 5% 8,0,, 2 5% Al,0,, the sum of 8,0, and ALO,

become poor if the amounts of these additional glassforming materials exceed the ranges specified.

Generally, phosphate glass is most stable when the molar ratio of the glass modifiers to the glass-forming materials is about 4 6. If the amounts of the -glass- 5 shown:

forming materials exceed this ratio, the stability of the glass tends to be worsened, and insmaller amounts, the

' chemical durability of the glass tends to become poor. However, this can be improved by the proper choice of modifiers. Extensive investigation revealed that the use 10 of BaO,-MgO, ZnO, CaO, SrO and As,0 givegood resuits. BaO is effective for improving the fusibility, stability and chemical durability of the glass. MgO

j ZnO serve to prevent the coloration caused by When the amount of P 0 is large glass. ZnO also serves to improve the stability or chemical durability thereof. CaO improves the chemical stability, and increases the stability of the glass when used conjointly with MgO. SrO contributes to the improvement of chemical durability or stability especially when the amount of P 0, is relatively small. As,0, also helps to prevent the coloration caused by Ti. These glass modifiers prove effective when used in the amounts specified above Glass comprising, by we bility and durability since it has a large Abbes number (50.2 66.0) and a relatively high 0., (0.443 0.493).

Example No.

aroorzuoaiiuetzodotau DOQGOOODOOOOOOOOOOOUO mmmwmwmmmmwwmmfi aoonauuuoduoeoz w .a a mwm geaeaawwn aaasmssxs amunneeeanm sin nawawwaaeaawmwwnannnm i7 a8 77 7? 7 7.7 BHNBBH uewmmwannwmnannaaaaan mmnnnneoeo ms mmmmnmmnnnnn s anus.

iii

SrCO;

mums.

some

mmmw

man

SrO A302 T10;

2110 CaC) TABLE 2 Ingredient oxides (percent by weight) Lt Da Coloration Do Do Do Do Do 00500OM50005000 5000000 500 1 l0L23 0L230LZ& 0L1&L2& .0 L1

aawmawwmm TABLE 3 Continued It is seen from the above table that according to the present invention, an anomalous dispersion glass having a large Abbes number and a-large partial dispersion in a short wavelength region is obtained, which at the What is claimed is:

l. A colorless anomalous dispersion glass free of alkali metal oxides and having a large Abbes number consisting of, in percentages by weight, calculated as 2. The glass according to claim 1 which has an Abbes number of from 4-5 to 70 and a partial dispersion ratio 0, of from 0.430 to 0.505.

3. The glass according to claim 1 consisting of from 50 to 70% 150,, from 1 to 5% 8,0,, from 2 to 5% Al- 0,, wherein the sum of the amount of said B 0, and

4. The glass according to claim 3 which as a v of from 50.2 to 66.0 and a 0, of from 0.443 to 0.493.

5. A colorless anomalous dispersion glass free of alkali metal oxides and having a large Abbes number and As,0, is to and from 0.05 to 4.0%, based on the total weight of said glass-forming'materials and said glass modifiers of TiO,, said amount of TiO, providing an anomalous dispersion without decreasing the Abbe's number of said glass.

A1 0, is from 3 to 8% and from 0.5 to 2.5% TiO,, all percentages being by weight.

consisting of, in percentages by weight, calculated as P,O,, from 1.0 to 5.0% B,O, and from 1 to 10% A1,0, as glass-forming materials, wherein the sum of the amount of said 8,0, and Al,0, is from 2 to 15%, said amount of A1 0,, and B 0, preventing coloration in said glass; from 4 to 38% BAO, from 2 to 17% MgO, from 0 to 10% ZnO, from o to 8% CaO, from 0 to 10% SrO and from 0 to 3% Asp, as glass modifiers, wherein the sum of the amount of said 8210, MgO, ZnO, CaO, SrO

Example same time, is colorless and has superior stability, fusibility and chemical durability.

the component oxides of said glass, from 38 to 0on000 55550000000000000000 0 aaaaasaee N wznwzmwmm 5 O 5 0 H m 3 4 4 5 5 W )llll l f f S. fo t 00((i1(00.100000000000006666 a g f 8 82 V I r ouaxaanfiafiv atstassia 7 7 7 7 m M m n W m m m 0 N w m mh e a 3 a nm .n N w 11 0 f.l 6 t p e W m M noenpg vll mda sa a m CH r. e n mm m fl m hfi m .m hhc mu 1 m l w) m Z r-h E m tw lc fi pd C 000001555550000000000.0242. L2 S n a h 3SmmOm u G 111zlzsaaaaaoeasssssmmm m mm m .e Tw m mw m H a CH an dh .Ittt 8 h .lh D m hum mmw mnmmnm m w wm .m l 5 6 e nnnt w o n aejfim m mw nfl x "Mm, um m wm m e um mm m m db s m wwmmmmmmmmmwwmwmuuun mwww b so E re meb n m fi n umhn t .w s w mz m w m mm P .4 m w m a w 0 L 5 Off. ts .1 nv Tm 2r tl O2 QZSCOR m mdhT- b 555555555555555000000000000 .1 a rrfi e nflodhnw Um a.m 0ae0X. .m 3 T m oA m n m md a a m m m m m d m m m e e a E g f h o s V a old 6 hl l I h r s m le lT ehu P tP B a sm wwm nm mm m mnai m m m: m 555555555555555555556660000 "MD- fldhfl nmmmpu nthwd dl l. 1 1 LLLLLLLLLLLLLzzazzaaazzzz w m m m a l d 8 m .M. s s fl t m m .m e m mm .m e TA m m m mw k m e a e s s PM h a $5.1 am n fi mmfim s m ii iiii )1), e l i it o l o .mmnoxuuuunxJlxumm jaAamobb h mm .0T m w e Mm wh m m 0 w w l m T m am t a e m mmmmmmmmmmmmmmmmwmmmmmmmwmw e t a m m e a a Pm n m c m w m in .m mm a r a U 1111111111 m.m flm d m cww 2 e .w. v h d iuwm3 (am mn wswmmm h mm ew u w m mma wmema mmw mey hew lw mm m u l pd r. g u 9:! u T e Ol Tum v n h "6.0 n .1 1 nhwn hhn au w mmmm W fim m u hm fl fl hm-mbmflm eam v. 8 u m 0 W mp me.m phmpg a tlt CStmunaCaO n RN 7 the component oxides of said glass, from 40.0 to 67.4% P from 1.5 to 3.6% 8,0 and from 1 to 9.0% A1 0 as glass-forming materials, wherein the sum of the amount of said B 0, and A1 0, is from 3 to 12.6%, said amount of A1 0 and 13,0 preventing coloration in said glass; from 4.3 to 37.9% BaO, from 2.0 to 13.2% MgO, from 0 to 10.0% ZnO, from 0 to 9.5% SrO, from 0 to 6% Ca() and from 0 to 2.5% As,0, as glass modifiers, wherein the sum of said 8210, MgO, ZnO, SrO, C210 and As,0 is from 20.0 to 57.0%; and from 0.05 to 3.0% based on the total weight of said glass-forming materials and glass modifiers, of TiO,, said amount of TiO, providing an anomalous dispersion without decreasing the Abbes number of said glass, and said amounts of MgO, Ar o; and ZnO also serving to prevent coloration in said glass.

6. Theglass according to claim 5 which has a v of from 50.2 to 67.9 and a 0,, of from 0.436 to 0.503.

7. in an anomalous dispersion glass consisting essentially of 9,0, as a basic glass-forming material and H0, as an additive to obtain an anomalous dispersion, wherein large quantities of alkali metal oxides are added thereto to prevent coloration in said glass, resulting in a glass of poor stability and chemical durability. the improvement consisting of a colorless anomalous dispersion glass free of alkali metal oxides and having an Ahbes number of from 45 to 70, a partial dispersion ratio 0,, of from 0.430 to 0.505, and good stability and chemical durability, said glass consisting of, in percentages by weight, calculated as the component oxides of said glass, from 38 to P,O from 1.0 to 5.0 B 0 and from 1 to 10% A1 0 as glass -forming materials, wherein the sum of the amount of said B 0 and A1 0 is from 2 to 15%, said amount of A1,0, and B 0; preventing coloration in said glass; from 4 to 38% BaO, from 2 to 17% MgO, from 0 to 10% ZnO,-from 0 to 8% CaO, from 0 to 10% SrO and from 0 to 3% A5 0 as glass modifiers, wherein the sum of the amount of said BaO, MgO, ZnO, CaO, SrO and A5 0; is 15 to 60%, said amount of M30, As,0, and ZnO also serving to prevent coloration in said glass; and from 0.05 to 4.0%,

'l'iO, providing an anomalous dispersion without decreasing the Abbes number of said glass.

*- i i i t 

2. The glass according to claim 1 which has an Abbe''s number of from 45 to 70 and a partial dispersion ratio theta hg of from 0.430 to 0.505.
 3. The glass according to claim 1 consisting of from 50 to 70% P2O5, from 1 to 5% B2O3, from 2 to 5% Al2O3, wherein the sum of the amount of said B2O3 and Al2O3 is from 3 to 8% and from 0.5 to 2.5% TiO2, all percentages being by weight.
 4. The glass according to claim 3 which as a Nu d of from 50.2 to 66.0 and a theta hg of from 0.443 to 0.493.
 5. A colorless anomalous dispersion glass free of alkali metal oxides and having a large Abbe''s number consisting of, in percentages by weight, calculated as the component oxides of said glass, from 40.0 to 67.4% P2O5, from 1.5 to 3.6% B2O3 and from 1 to 9.0% Al2O3 as glossforming materials, wherein the sum of the amount of said B2O3 and Al2O3 is from 3 to 12.6%, said amount of Al2O3 and B2O3 preventing coloration in said glass; from 4.3 to 37.9% BaO, from 2.0 to 13.2% MgO, from 0 to 10.0% ZnO, from 0 to 9.5% SrO, from 0 to 6% CaO and from 0 to 2.5% As2O3 as glass modifiers, wherein the sum of said BaO, MgO, ZnO, SrO, CaO and As2O3 is from 20.0 to 57.0%; and from 0.05 to 3.0% based on the total weight of said glass-forming materials and glass modifiers, of TiO2, said amount of TiO2 providing an anomalous dispersion without decreasing the Abbe''s number of said glass, and said amounts of MgO, As2O3 and ZnO also serving to prevent coloration in said glass.
 6. The glass according to claim 5 which has a Nu d of from 50.2 to 67.9 and a theta hg of from 0.436 to 0.503.
 7. In an anomalous dispersion glass consisting essentially of P2O5 as a basic glass-forming material and TiO2 as an additive to obtain an anomalous dispersion, wherein large quantities of alkali metal oxides are added thereto to prevent coloration in said glass, resulting in a glass of poor stability and chemical durability, the improvement consisting of a colorless anomalous dispersion glass free of alkali metal oxides and having an Abbe''s number of from 45 to 70, a partial dispersion ratio theta hg of from 0.430 to 0.505, and good stability and chemical durability, said glass consisting of, in percentages by weight, calculated as the component oxides of said glass, from 38 to 70% P2O5, from 1.0 to 5.0 B2O3 and from 1 to 10% Al2O3 as glass -forming materials, wherein the sum of the amount of said B2O3 and Al2O3 is from 2 to 15%, said amount of Al2O3 and B2O3 preventing coloration in said glass; from 4 to 38% BaO, from 2 to 17% MgO, from 0 to 10% ZnO, from 0 to 8% CaO, from 0 to 10% SrO and from 0 to 3% As2O3 as glass modifiers, wherein the sum of the amount of said BaO, MgO, ZnO, CaO, SrO and As2O3 is 15 to 60%, said amount of MgO, As2O3 and ZnO also serving to prevent coloration in said glass; and from 0.05 to 4.0%, based on the total weight of said glass-forming materials and said glass modifiers, of TiO2, said amount of TiO2 providing an anomalous dispersion without decreasing the Abbe''s number of said glass. 